Known ski boots of this types are generally provided with relative "aft to fore" flexibility, at the portion adjacent the kick region, in order to permit deflection of the leg of the skier with respect to the ankle in case of pressures applied on the sole of the boot. In effect, it has been realized that, during the normal practice of downhill skiing, and particularly in competition, certain stresses were susceptible of causing tripping of the safety bindings of the ski, while controlled flexion the upper of the said boot sufficed to compensate thenm, and this without danger to the skier. It is for this reason that, in most of the known ski boots, the flexure zones have been arranged at a distance from the points of articulation between the base of the shell and the upper; generally the flexure is controlled either by elastic deformation of a portion of the boot, or through the intermediary of an elastic device offering a certain resistance, sometimes progressive, to inclination of the upper toward the front of the boot.
In all these boots, it has appeared necessary to form perfect joints between the constituent elements susceptible to displacement relative to one another during flexures of the upper, while retaining optimal sliding quality compatible with the restraints and pressures to which they were subjected. It is thus that these boot elements, base of the shell, upper and/or flap are made, first, of materials having very good mechanical characteristics, and second, with forms obtained by molding and/or by machine finishing, specific to the joints to be produced. These boots turn out to be difficult to manufacture, due to the fact that the sliding zones must be prepared prior to mounting of the different parts of the boots, that their particular forms require more or less complex and expensive molding and/or machine finishing processes, and that the materials used have a higher cost than those which can be used for the rest of the other parts of the boot not subjected to such particular and elevated stresses.
This is the case with the boot described in U.S. Pat. No. 4,095,356. In effect, the upper of the boot, connected to the base of the shell by means of pivots, is articulatedly mounted on the latter with a degree of limited freedom of deflection by a resilient device interposed between them. The sliding zones are obtained in this case in monobloc fashion respectively with the upper and the base of the shell, and tightness is assured by the resilient device introduced into the housings also provided in the upper and the base of the shell. On the other hand, according to French Pat. No. 2,256,734, the sliding zones are obtained on the portion adjacent to the kick region, respectively on the upper and the base of the shell, in such manner as to overlap one another, and a resilient device, assuring the connection between the said upper and the base of the shell, enables control of the flexibility.